05000346/LER-1981-026-03, /03L-0:on 810428,reactor Protection Sys Channel 1 Tripped on Flux/Delta Flux/Flow.Caused by Failure of Flow Differential Pressure Transmitter Primary Power Transformer Shorting to Ground.New Amplifier Installed & Calibr
| ML20004C112 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 05/26/1981 |
| From: | Werner J TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20004C109 | List: |
| References | |
| LER-81-026-03L, LER-81-26-3L, NUDOCS 8106010534 | |
| Download: ML20004C112 (3) | |
| Event date: | |
|---|---|
| Report date: | |
| 3461981026R03 - NRC Website | |
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U.S. NUCLEAR REGULATERY COMMISSION NRC FORM 366 87 77)
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60 61 DOCK ET NUVS ER 68 69 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROB A BLE CONSEQUENCES h ITTTl I (NP-33-81-28) On 4/28/81 at 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br />, Reactor Protection System (RPS) Channel 1 l
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11 i O I l The cause of this occurrence was the failure of the flow differential pressure trans-lmitter pricary power transformer shorting to ground and causing the transmitter ampli-l i i l fier output to go low.
Under WO IC-405-81, a new amplifier assembiv was installed I
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(419) 259-5000, Ext. 231?
John Werner PHONE:
DVR 81-057 NAVE Of PREPARER a
o TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-81-28 DATE OF EVENT: April 28, 1981 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Channel 1 Reactor Coolant Flow Signal to the Reactor Protection Systea (RPS)
Conditions Prior to Occurrence: The unit was in Mode 1 with Power (MWT) = 2550 and Load (Gross MRE) = 836 Description of Occurrence: On April 28, 1981.at approximately 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br />, RPS Channel 1 tripped on flux / delta flux / flow.
Investigation revealed that the Chan-nel 1 Loop A flow signal had failed to zero. Loop A flow on all other channels indicated normal flow conditions. This placed the unit in Action Statement 2 of Technical Specification 3.3.1.1, which required the intnerable channel to be placed in a tripped condition. The channel was declarea inoperable, and the chan-nel left in the tripped condition.
. Designation of Apparent Cause of Occurrence: The apparent cause of this occurrence was the failure of the flow transmitter primary power transformer shorting to ground and causing the transmitter amplifier output to go low.
Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. Reactor coolant flow'did not vary, only one of eight differential pressure transmitters failed.
Corrective Action
Maintenance Work Order IC-405-81 was issued for repair. Inves-tigation revealed icw resistance readings to ground on both 115 VAC power leads to the transmitter (one lead read approximately 20 ohms to ground and the other lead read approximately 100 ohms to ground). Unit power was decreased to 10%, the trans-mitter was removed from containment, a new amplifier assembly installed and cali-I brated, and the transmitter re-installed and put into servf.ce. A time response and calibration check per ST 5030.05 were satisfactorily performed, and the channel declared operable at about 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on May 3, 1981, thus removing the unit from the action statement of Technical Specifciation 3.3.1.1.
The failed flow transmitter was a Bailey BY differential pressure transmitter, which has a history of a high failure rate.
Facility Change Faquest 78-525 has been approved for implementation and will replace all Bailey transmitters in containment with Rosemont detectors. This was not done at this time because the new transmitters have not yet been received from Rosemont. The failed Bailey amplifier aasembly did have its primary transformer winding shorted to ground, and the transformer did show some discoloration due to possible overheating.
LER #81-026
TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-81-28 PAGE 2 Failure Data: There have been two previous failures of reactor cooiant flow trans-mitters, see Licensee Ovent Reports NP-33-78-24 and NP-33-78-117.
LER #81-026 e
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